Ok, a few things...
First, "the backpack thing" you're referring to is a hydration system (like Camelback), not a backpack. Do you want a backpack or a hydration system?
Secondly, the vest (which looks like a sort of TT TAC-1A rifleman vest knockoff, except with PALS webbing on the pack) has 6 double mag pouches (so 12 mags) and you're adding a sort of subload mag carrier... but unless you already have mags, you'll have 1 locap + 2 midcaps...?
The kneepads, I suggest getting real kneepads, since they'll be protecting real knees from real abuse. Dunno how good the KA ones are. I like Altas myself. Maybe someone else can comment on the KA kneepads.